The patch titled
gcov: exclude code operating in userspace from profiling
has been added to the -mm tree. Its filename is
gcov-exclude-code-operating-in-userspace-from-profiling.patch
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------------------------------------------------------
Subject: gcov: exclude code operating in userspace from profiling
From: Peter Oberparleiter <oberpar@xxxxxxxxxxxxxxxxxx>
Fix for this issue on x86_64:
rostedt@xxxxxxxxxxx wrote:
> On bootup of the latest kernel my init segfaults. Debugging it,
> I found that vread_tsc (a vsyscall) increments some strange
> kernel memory:
>
> 0000000000000000 <vread_tsc>:
> 0: 55 push %rbp
> 1: 48 ff 05 00 00 00 00 incq 0(%rip)
> # 8 <vread_tsc+0x8>
> 4: R_X86_64_PC32 .bss+0x3c
> 8: 48 89 e5 mov %rsp,%rbp
> b: 66 66 90 xchg %ax,%ax
> e: 48 ff 05 00 00 00 00 incq 0(%rip)
> # 15 <vread_tsc+0x15>
> 11: R_X86_64_PC32 .bss+0x44
> 15: 66 66 90 xchg %ax,%ax
> 18: 48 ff 05 00 00 00 00 incq 0(%rip)
> # 1f <vread_tsc+0x1f>
> 1b: R_X86_64_PC32 .bss+0x4c
> 1f: 0f 31 rdtsc
>
>
> Those "incq" is very bad to happen in vsyscall memory, since
> userspace can not modify it. You need to make something prevent
> profiling of vsyscall memory (like I do with ftrace).
Signed-off-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Reported-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Tested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/Makefile | 2 ++
1 file changed, 2 insertions(+)
diff -puN arch/x86/kernel/Makefile~gcov-exclude-code-operating-in-userspace-from-profiling arch/x86/kernel/Makefile
--- a/arch/x86/kernel/Makefile~gcov-exclude-code-operating-in-userspace-from-profiling
+++ a/arch/x86/kernel/Makefile
@@ -26,6 +26,8 @@ CFLAGS_tsc.o := $(nostackp)
CFLAGS_paravirt.o := $(nostackp)
GCOV_PROFILE_vsyscall_64.o := n
GCOV_PROFILE_hpet.o := n
+GCOV_PROFILE_tsc.o := n
+GCOV_PROFILE_paravirt.o := n
obj-y := process_$(BITS).o signal.o entry_$(BITS).o
obj-y += traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
_
Patches currently in -mm which might be from oberpar@xxxxxxxxxxxxxxxxxx are
origin.patch
gcov-exclude-code-operating-in-userspace-from-profiling.patch
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